Musical Mod Lets MRI Scanner Soothe the Frazzled Patient

Hackers love to make music with things that aren’t normally considered musical instruments. We’ve all seen floppy drive orchestras, and the musical abilities of a Tesla coil can be ear-shatteringly impressive. Those are all just for fun, though. It would be nice if there were practical applications for making music from normally non-musical devices.

Thanks to a group of engineers at Case Western Reserve University in Cleveland, there is now: a magnetic resonance imaging machine that plays soothing music. And we don’t mean music piped into the MRI suite to distract patients from the notoriously noisy exam. The music is actually being played through the gradient coils of the MRI scanner. We covered the inner working of MRI scanners before and discussed why they’re so darn noisy. The noise basically amounts to Lorenz forces mechanically vibrating the gradient coils in the audio frequency range as the machine shapes the powerful magnetic field around the patient’s body. To turn these ear-hammering noises into music, the researchers converted an MP3 of [Yo Yo Ma] playing [Bach]’s “Cello Suite No. 1” into encoding data for the gradient coils. A low-pass filter keeps anything past 4 kHz from getting to the gradient coils, but that works fine for the cello. The video below shows the remarkable fidelity that the coils are capable of reproducing, but the most amazing fact is that the musical modification actually produces diagnostically useful scans.

Our tastes don’t generally run to classical music, but having suffered through more than one head-banging scan, a half-hour of cello music would be a more than welcome change. Here’s hoping the technique gets further refined.

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Daphne Oram and the Birth of Electronic Music

For most of human history, musical instruments were strictly mechanical devices. The musician either plucked something, blew into or across something, or banged on something to produce the sounds the occasion called for. All musical instruments, the human voice included, worked by vibrating air more or less directly as a result of these mechanical manipulations.

But if one thing can be said of musicians at any point in history, it’s that they’ll use anything and everything to create just the right sound. The dawn of the electronic age presented opportunities galore for musicians by giving them new tools to create sounds that nobody had ever dreamed of before. No longer would musicians be constrained by the limitations of traditional instruments; sounds could now be synthesized, recorded, modified, filtered, and amplified to create something completely new.

Few composers took to the new opportunities offered by electronics like Daphne Oram. From earliest days, Daphne lived at the intersection of music and electronics, and her passion for pursuing “the sound” lead to one of the earliest and hackiest synthesizers, and a totally unique way of making music.

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See Cells In A New Light With A DIY Fluorescence Microscope

Ever since a Dutch businessman peered into the microscopic world through his brass and glass contraption in the 1600s, microscopy has had a long, rich history of DIY innovation. This DIY fluorescence microscope is another step along that DIY path that might just open up a powerful imaging technique to amateur scientists and biohackers.

In fluorescence microscopy, cells are treated with various fluorescent dyes that can be excited with light at one wavelength and emit light at another. But as [Jonathan Bumstead] points out, fluorescence microscopes are generally priced out of the range of biohackers. His homebrew scope levels the playing field a bit. The trick is to use 3D-printed parts to kit out commonly available digital cameras – a USB microscope, a DSLR, or even a smartphone camera. Excitation is provided by a ring of Nexopixel LEDs, while a movable rack holds a filter that blocks the excitation wavelength but allows the emission wavelength to pass through to the camera. He demonstrates the technique by staining some threads with fluorescent ink from a highlighter marker and placing them on a sheet of tissue paper; in conventional bright-field mode, the threads all but disappear into the background, but jump right out under fluorescence.

Ith’s true that the optics are not exactly lab quality, and the microscope is currently only set up to do reflectance imaging as opposed to the more typical transmissive mode where the light passes through the sample. That’s an easy fix, though, and reflectance mode is still useful. We’ve seen fluorescence microscopy get quite complex before, but this simple scope might be enough to get a biohacker started.

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Fail of the Week: How Not to Design an RF Signal Generator

We usually reserve the honor of Fail of the Week for one of us – someone laboring at the bench who just couldn’t get it together, or perhaps someone who came perilously close to winning a Darwin Award. We generally don’t highlight commercial products in FotW, but in the case of this substandard RF signal generator, we’ll make an exception.

We suppose the fail-badge could be pinned on [electronupdate] for this one in a way; after all, he did shell out $200 for the RF Explorer signal generator, which touts coverage from 24 MHz to 6 GHz. But in true lemons-to-lemonade fashion, the video below he provides us with a thorough analysis of the unit’s performance and a teardown of the unit.

The first step is a look at the signal with a spectrum analyzer, which was not encouraging. Were the unit generating a pure sine wave as it should, we wouldn’t see the forest of spikes indicating harmonics across the band. The oscilloscope isn’t much better; the waveform is closer to a square wave than a sine. Under the hood, he found a PIC microcontroller and a MAX2870 frequency synthesizer, but a conspicuous absence of any RF filtering components, which explains how the output got so crusty. Granted, $200 is not a lot to spend compared to what a lab-grade signal generator with such a wide frequency range would cost. And sure, external filters could help. But for $200, it seems reasonable to expect at least some filtering.

We applaud [electronupdate] for taking one for the team here and providing some valuable tips on RF design dos and don’ts. We’re used to seeing him do teardowns of components, like this peek inside surface-mount inductors, but we like thoughtful reviews like this too.

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A Guide To Audio Amps For Radio Builders

For hams who build their own radios, mastering the black art of radio frequency electronics is a necessary first step to getting on the air. But if voice transmissions are a goal, some level of mastery of the audio frequency side of the equation is needed as well. If your signal is clipped and distorted, the ham on the other side will have trouble hearing you, and if your receive audio is poor, good luck digging a weak signal out of the weeds.

Hams often give short shrift to the audio in their homebrew transceivers, and [Vasily Ivanenko] wants to change that with this comprehensive guide to audio amplifiers for the ham. He knows whereof he speaks; one of his other hobbies is jazz guitar and amplifiers, and it really shows in the variety of amps he discusses and the theory behind them. He describes a number of amps that perform well and are easy to build. Most of them are based on discrete transistors — many, many transistors — but he does provide some op amp designs and even a design for the venerable LM386, which he generally decries as the easy way out unless it’s optimized. He also goes into a great deal of detail on building AF oscillators and good filters with low harmonics for testing amps. We especially like the tip about using the FFT function of an oscilloscope and a signal generator to estimate total harmonic distortion.

The whole article is really worth a read, and applying some of these tips will help everyone do a better job designing audio amps, not just the hams. And if building amps from discrete transistors has you baffled, start with the basics: [Jenny]’s excellent Biasing That Transistor series.

[via Dangerous Prototypes]

Algae On Your Plate

For those of us who grow up around natural swimming holes, algae are the reason we have to wash after taking a dip. Swimmer’s itch* or just being covered in green goop is not an attractive way to spend an afternoon. Lumping all algae together is not fair, some of it is nasty but some of it is delicious and humans have been eating it for generations.

If you are thinking that cases of algae cuisine are not widespread and that algae does not sound appealing, you are not alone. It is a tough sell, like convincing someone to try dandelions for the first time. It may not warrant a refrigerator section in the grocery store yet, but algae can produce protein-rich food which doesn’t require a lot of processing.

Currently, there is a lot of work to be done to bring up the efficiency of algae farms, and Qualitas has already started. The leaps they are making signify just how much room we have for improvement. The circulating paddle wheels, which can be seen in the video below the break, use one-third of the energy from their previous version. Their harvester uses one-thirtieth! Right now, their biggest cost comes from tanks of carbon dioxide, which seems off given that places such as power plants pay to get rid of the stuff. That should give some food for thought.

The 2018 Hackaday prize could use some algal submissions and you could take that to the bank. Ready to start growing your own algae, automate the process. It may also keep you from tripping while walking to the grocery store, or you can print with it.

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